I'm going to put my original write up for d20 Modern (minus stats) in a reply...maybe two dependent on character limit
Changes for Dresdenverse:
The Arachnae of Arachnae Bioware are actually descended from a variety of spider-based scions and spirit folk. Primarily these would be shapechanging goblin-spiders that escaped their eradication at the hands of the samurai in Japan and ended up breeding with humanity in Russia and China. Up until recently, the heritage has remained muted, but some magical effect has, in the recent past caused them to express into a large group of scions and changelings. While the Chinese/Russian ethnic groups are strongest, the Arachne would consider spider-scions that hale from descent of the Greek Arachne as well as the African Anansi spirit as well as others. In fact, the Arachne as a whole probably lack enough supernatural knowledge to know precisely what they are.
Alignment in Dresdenverse: In general, a basically isolationist neutral, neither wanting to harm those around them or stick their neck out to help others. Katya Chin's connections with humans means that her faction might be a bit more leaning toward taking part in the world. Ms Chin would almost be a mirror of Marcone in attitude, willing to kill to protect her people and work behind the scenes as well as make alliances. Some of the other factions of the Arachnae are more likely to follow one of these philosophies: total isolation, interaction in secret (currently most popular), pre-emptive attacks, cooperation.
Power Scale in Dresdenverse: They'd be big enough to get in the news occasionally, but not so big or in fad that people really pay them much attention. They probably have more of a public splash than Monoc due to their background in fashion, but less of an impact in business and supernatural affairs. They are not heavy hitters overall...maybe Fellowship of St. Giles level power.
Templates:
Face
Faces appear to the naked eye as if they are as human as everybody else save for some mild differences. They are the Arachne most end up dealing with. Faces are not the most common Arachne, and are in fact rather uncommon, but they are the ones that handle the human employees that the Arachne must deal with now. Katya Chin is a face and the current recognized leader by most of the Arachne, though some believe that she is a figurehead and get annoyed when she acts otherwise. Faces tend to have an urge to prove themselves useful and often interact with humanity on a more regular business. Most of Katya Chin's assassination teams are faces, for example. As such, despite lacking some of the same level of power as their relatives, it is the faces who can be considered the most dangerous of the species.
Musts: A high concept that describes their species such as "Arachne Assassin" or "Public Face of the Arachne" or something of the sort.
Spider Walk (-1)
Spinnerettes/Webbing, bought as Rituals focused on Crafting: webbing (-2)
Options:
Some faces may have learned combat applications of their webbing, buy that as Channelling: Webbing (-2)
Important Skills: Deceit and Empathy are highly important to faces for the most part, other skills will show up based on their specific task (assassin, manager, public relations, celebrity, etc)
Minimum Refresh Cost: -3
Weaver
Weavers have two human eyes with red irises and six eye-spots set in pairs up from their forehead. The first feature most people notice about them, however, are their six-arms. Weavers are the calmest of the Arachne and tend to be split between crafters and spiritual leaders. They come across as very friendly, even if they dislike a person.
Musts: Must have a high concept that relates to their species or breed. "Arachne Priest" or "Weaver Philosopher"
Spider Walk (-1)
The Sight (-1)
Webbing crafting as per Faces (-2)
Options: Some Weavers might be have true talent in the magical arts or else you can say their spirituality comes from True Faith abilities.
Important Skills: Rapport and Conviction, in addition levels of Fists or Might might represent the advantage of having multiple arms.
Minimum Refresh: -4
Hunters
Hunters have thick skin that invariably gives them the appearance of being heavily muscled. They are incredibly strong and have large, multi-faceted eyes. They tend to have a large variety of skin colorations, including mutli-colored patterns. Hunters, like most Arachne, are private about their life, in addition they are reserved and very cautious. They are also aggressively protective of people they consider friends.
Musts: Must have a high concept that relates to their species or the company. "Heavy Hitter for Arachne Security" or "Hunter Bodyguard"
Spider Walk (-1)
Claws (-1)
Inhuman Strength (-2)
Inhuman Toughness (-2)
Catch: Toxins (+1)
Options: Some might be venomous.
Important Skills: Endurance, Alertness, some combat skills
Minimum Refresh: -5
Spiders
Spiders have the upper body a human being and the lower body of a spider. They tend to be hyperactive, very tactile and affectionate. They are the most bizarre, by human standards, in both mind and body. Spiders have little concept of tact and are rarely disturbed by anything. The majority have a very scientific outlook and a fervent interest in the natural world. Several claim they can understand spiders, insects and other such creatures and seem to have an empathic connection with them.
Musts: Must have a high concept that relates to their species such as "Spider Mortician" or "Hive Mistress"
Echoes of the Beast (-1)
Webbing as Faces (-2)
Spider-walk (-1)
Inhuman Speed (-2)
Claws: Venomous (-3)
Options: Some might eventually learn to manipulate their insects and spiders more completely via magic of some kind and gain Channeling or Rituals in that regard. Others might learn combat applications of their webbing as Faces and Weavers can.
Important Skills: Lore and Scholarship, learning is their primary desire, Survival might also represent their naturalistic attitude.
Minimum Refresh: -9